There are a number of mechanisms for automatically dispensing fluids, such as deodorants, disinfectants, insecticides and the like. One such mechanism uses a synchronised motor to periodically operate an aerosol dispenser. Another type uses the movement generated by the withdrawal of a towel from a towel dispenser to mechanically drive a fan to move air over a block of deodorant and into a room. Other types use the motion of a door to operate a mechanical drive which moves air across a deodorant and into a room. Yet others use special mechanical linkages such as toggles and bellows to operate valves and aerosol devices. Typically, the mechanism operated by the motion of an associated door causes the fluid to be dispensed each time the door is opened and/or closed, which is often more frequently than is required. Too frequent dispensing of the fluid, especially pesticides, insecticides and other harmful substances may be undesirable and injurious to persons working in the area; when used in and near a kitchen or other food-preparing facility there is a danger of contamination of the food being prepared. Some devices are operated by an electric motor or some other means which requires a more expensive and complex arrangement.